Gas fired infrared radiation emitters are widely used in the pulp and paper industry for the drying of coatings on moving cellulosic webs. These emitters are well known; thus, for example, one such emitter is described in U.S. Pat. No. 5,820,361 of Daniel M. Lavigne et al.
The prior art infrared radiation emitters often contain a reverberating screen (or "grating") which increases the radiant power output of the emitter while simultaneously protecting the primary radiating surface from contamination. In some of the prior art embodiments, the screen is integrally connected to the emitter; thus, in these embodiments, when the screen fails due to excessive temperature, contamination, and/or normal wear and tear, the entire emitter must be replaced. When this occurs, not only must one bear the expense of a brand new emitter, but one loses a substantial amount of production time while replacing the emitter.
In the device disclosed in Belgium patent 09501070, an emitter with a removable grating is disclosed (see, e.g., column 1 of U.S. Pat. No. 5,820,361). However, as the patentees of U.S. Pat. No. 5,820,361 disclosed, the device of such Belgium patent was essentially inoperable in that "During tests at high temperatures this radiant however exhibited a risk of the grating falling, such fall then necessitating stopping the drying installation" (see lines 29-31 of Column 1 of U.S. Pat. No. 5,820,361).
The expressed objective of U.S. Pat. No. 5,820,361 is to remedy the screen falling problem. Thus, at lines 10-40 of Column 7 of such patent, it is disclosed that "The heat emitter . . . represented in FIGS. 1 through 4 has numerous advantages . . . . These advantages are . . . The risk of the screen or grating falling is almost nil."
However, despite this expressed objective, none of the embodiments depicted in this patent in fact contained a removable screen which did not fall during high temperature use. Heat emitters corresponding to the claimed embodiments in this patent were sold by IDS International, Inc. of Windsor Locks, Conn. under the name of "OPTIRAY GAS EMITTER"; however, during high temperature use of these emitters (in excess of 2,000 degrees Fahrenheit), a substantial number of the removable screens on such emitters invariably fell off.
In applicant's copending U.S. patent application U.S. Ser. No. 09/193,183, there is disclosed a gas fired infrared emitter with a removable screen which does not fall off during high temperature use. This particular emitter can be used with our without a screen; and it is an object of this invention to disclose a whole range of emitters with removable screens, each of which can be used with or without a screen.
In applicant's copending U.S. patent application U.S. Ser. No. 09/280,427, there is disclosed a gas fired infrared emitter which is comprised of an emitter body provided with a diffuser for distributing a fuel-oxygen containing gas mixture, a specified primary radiating surface, and a screen removably connected to such emitter body.
The emitters disclosed in patent applications U.S. Ser. Nos. 09/280,427 and 09/193,183 are substantial improvements over the prior art emitters. It is an object of this invention to provide a novel emitter which, in addition to containing the novel features described in applicant's copending patent applications, also contains novel and reliable means for detecting when the emitters are combusting gas.